1. Field of the Invention
The present invention relates to cranes and more particularly relates to reversible outrigger supports for varying the lifting capacity of the crane depending upon the orientation of the outrigger supports.
2. Description of the Prior Art
The use of outriggers to provide stability to a crane or similar machine is well known. Also, power-operated ground-engaging jacks have been used at the outer end of outrigger arms.
Cranes that are used in heavy construction work are fairly large units and the movement of such members from job site to job site is difficult and expensive. It is therefore desirable that a single crane be capable of a fairly large range of lifting capacities so that additional cranes need not be brought to the site to take care of lifting operations beyond the range of the basic crane on the job. Also, of course, since cranes are expensive, they must be used frequently to justify their original purchase. An object of the present invention is to provide a crane capable of operating in several load ranges.
The use of outriggers to give added lifting stability to cranes is, of course, well known, as also is the use of power jacks mounted in the outer ends of the arms. Thus, at present, the lifting range of a basic crane at a job site can be increased somewhat by the attachment of outriggers. In accordance with the present invention, even further increases in the lifting capacity of a basic crane can be obtained by the use of outrigger units, not only to engage the ground to provide the above-mentioned increase in lifting capacity, but also to coact with members of heavy-duty attachments to make them operable with a basic crane and provide a heavy duty range of lifting capacity. In one type of heavy duty crane, an auxiliary frame is mounted on a basic crane and includes lifting members for raising the frame off the ground when the crane is moved from place to place. In the present invention, outrigger units carry out this auxiliary frame lifting function.